Barbieri Thesis - BioMedical Materials program (BMM)

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Chapter 6 – Fluid uptake as instructive factor Table 7. Statistical comparison of serum protein adsorption and fluid uptake after seven days in 0.1% FBS. The test used was one–way ANOVA test for means (Tukey’s) where a p–value smaller than 0.05 was considered as significant difference. MLD–MLDL MLD–MDL MLDL–MDL Serum protein adsorption Fluid uptake 10 –4 10 –4 >0.6 (no) 10 –3 0.7 (no) 6.3.5. Accelerated in vitro degradation of the composites Samples containing poly(D,L–lactide), i.e. MDL, could not be retrieved after five weeks as they broke down and fully fragmented. These samples had more swollen volume than MLD and MLDL after three weeks and could hardly keep their shape when touched with normal laboratory stainless steel spoons or tweezers. This indicated that MDL composites degraded and absorbed fluids faster. However, all three composites degraded during the 5–week period as indicated by their mass loss (Figure 7a), continuous release of calcium and phosphate ions (Figure 8). We observed that the apatite phase content decreased compared to the starting conditions (Table 6). In particular, samples containing PLD had the most stable mass, whereas MDL degraded most. Consistently, there was a direct link between mass loss and fluid uptake (Figure 7b), where the larger mass loss corresponded to a large fluid uptake and vice versa. A fast decline in intrinsic viscosity (and weight average molecular weight) was observed in MDL composites, followed by MLDL and MDL (Table 8). The degradation rate constants and the correlation coefficients are in Figure 9. The validity of the model to estimate the autocatalytic degradation rate is supported by the high values of the correlation coefficients. The results show that the polymer phase in MDL had a faster autocatalysed hydrolysis than MLDL and MDL, and in particular, this last result is in line with the fluid absorption trends confirming the important role fluid uptake has in degrading the polymer phase. Table 8. Measured inherent (inh) and intrinsic () viscosity, and weight average molecular weight (Mw) of the polymer phase over five weeks in PBS at 55°C. MLD MLDL MDL 0 weeks inh [dL g –1 ] [dL g –1 ] Mw [kDa] 0.60±0.01 0.61±0.01 43.5±0.9 0.48±0.01 0.49±0.01 42.9±0.9 0.44±0.01 0.45±0.02 51.5±1.4 1 week inh [dL g –1 ] [dL g –1 ] Mw [kDa] 0.51±0.03 0.52±0.02 34.5±1.7 0.30±0.02 0.30±0.01 22.7±0.3 0.20±0.01 0.20±0.01 17.5±1.1 3 weeks inh [dL g –1 ] [dL g –1 ] Mw [kDa] 0.36±0.02 0.36±0.01 20.4±0.6 0.23±0.01 0.24±0.02 16.1±0.7 0.10±0.02 0.11±0.01 7.3±0.8 134 5 weeks inh [dL g –1 ] [dL g –1 ] Mw [kDa] 0.32±0.01 0.33±0.01 16.9±0.5 0.14±0.02 0.15±0.01 8.8±0.3 not measured
Figure 7. Mass left (a) annd fluid uptake (b) of the threee composites ov ver five weeks accelerated a degradationn at 55C. Differennces are all signif ficative. Figure 8. (aa) Calcium and (bb) phosphate cum mulative ion conccentration over 5 weeks in PBS. ln( / ) 0 0 -0,2 -0,4 -0,6 -0,8 -1 -1,2 -1,4 -1,6 5 10 15 MLD MLDL MDL Timee (days) y = -0,07177x R² = 0,91441 Chapter 6 – Flu uid uptake as insstructive factor 20 25 300 35 y = -0,0196x R² = 0,9632 y = -0,03447x R² = 0,9252 Figure 9. AAutocatalysed hyd ln(/) against time 0.0717 dayy autocatalys valid in this –1 drolytic degradation rate constantt k obtained by linearly regressing e. The (absolute) rate constantss resulted 0.0196 day for the pollymer phases in MLD, MLDL and MDL res sed hydrolysis foor the polymer in MDL. The correelation coefficien experiment. –1 , 0.0347 pectively, indica nts R2 g the plot of day indicate th –1 and ating faster he model is 6.3.6. Surrface mineraliization After immmersion in SBFF, both ceramics (Figure 100) and all the composites c (F Figure 11) showed ssurface mineraalisation within n two days ass indicated by the formation of layers with irreggular shaped globules where apatite hhad spontane eously nucleated. It is interesting that, after mmineralisation n, the materiaals presented more nano–s structured surface teextures than their starting counterparts. In the case of ceramics, it can be observed that the precipitated apatite formedd globules, which w appare ently still maintaineed the initial diifference betw ween TCPS annd TCPB in the eir grain size. 135
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INSTRUCTIVE COMPOSITES FOR BONE REG
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INSTRUCTIVE COMPOSITES FOR BONE REG
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献给潘臻 A mamma e papà A Stef
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Summary Summary Developing new biom
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Summary containing 96%mol. L-lactid
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Samenvatting De behoefte aan een de
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Samenvatting structuur, bespoedigt
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Riassunto velocità di dissoluzione
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Riassunto generale, ha migliorato i
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Chapter 1 - Introduction 1.1. Eukar
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Chap pter 1 - Introducction Interst
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Chapter 1 - Introduction bone marro
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Chap pter 1 - Introducction Figure
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Chapter 1 - Introduction regenerati
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Chapter 1 - Introduction Key concep
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Chapter 1 - Introduction grown in c
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Chapter 1 - Introduction Mainly, th
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Chapter 1 - Introduction All these
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Chap pter 1 - Introducction materia
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Chapter 1 - Introduction protein, m
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CHAPTER 2 The role of gels in bone
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Chapter 2 - The role of gels in ins
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CChapter 2 - The role r of gels in
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CHAPTER 3 Instructive composites: e
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Chapter 3 - Instructive composites:
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Chapter 3 - Instructive compos site
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CChapter 3 - Instructive composit t
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CHAPTER 4 Controlling dynamic mecha
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Chapter 4 - Conntrol of mechanical
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Chapter 4 - Control of mechanical a
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Chapter 4 - Conntrol of mechanical
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Chapter 8 - General discussion can
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Chapter 8 - General discussion cons
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Chapter 8 - General discussion 8.1.
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Chapter 8 - General discussion rese
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References [1] Waggoner B. Eukaryot
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References induction of rank in ost
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References [72] Kokovay E, Wang Y,
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References [102] McBeath R, Pirone
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References molecule-mediated TGF- t
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References [159] Autumn K, Sitti M,
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References [189] Teixeira AI, McKie
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References [215] Tang L, Jennings T
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References [242] Wei G, Ma PX. Stru
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References [270] Atkinson BL, Hanks
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References [297] Sato I, Akizuki T,
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References hematopoietic stem cell
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References [352] Cullinane DM, Sali
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References [382] Norde W, Giacomell
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References differentiation of rat B
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Acknowledgments thank you for all t
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Acknowledgments desidero tutto il m
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Barbieri Thesis - BioMedical Materials program (BMM)

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